U.S. patent number 3,792,943 [Application Number 05/183,120] was granted by the patent office on 1974-02-19 for dry fiber distribution.
This patent grant is currently assigned to Ingenjorsfirma B-projekt Aktiebolag. Invention is credited to Jonas Anders Gote Helgesson.
United States Patent |
3,792,943 |
Helgesson |
February 19, 1974 |
DRY FIBER DISTRIBUTION
Abstract
Fibers are suspended in a rising stream of air which is
deflected into a distribution chamber having a bottom formed by a
belt-like, gas-permeable screen advanced over a suction box,
whereby a dry fiber web is produced on said screen. At the
deflection of the fiber-carrying air stream a second stream of air
is added to control the inflow of suspended fibers into the
distribution chamber and to cause the fibers to follow a trajectory
through said chamber. The pattern of fiber deposition on the moving
screen is further controlled by admitting additional air from above
through an adjustable opening in the enclosure of the distribution
chamber.
Inventors: |
Helgesson; Jonas Anders Gote
(Taby, SW) |
Assignee: |
Ingenjorsfirma B-projekt
Aktiebolag (Enebyberg, SW)
|
Family
ID: |
20298169 |
Appl.
No.: |
05/183,120 |
Filed: |
September 23, 1971 |
Foreign Application Priority Data
|
|
|
|
|
Oct 14, 1970 [SW] |
|
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13882/70 |
|
Current U.S.
Class: |
425/83.1; 19/304;
264/518; 19/300; 264/109; 425/141 |
Current CPC
Class: |
D04H
1/736 (20130101); D04H 1/732 (20130101); D04H
1/72 (20130101); B27N 3/14 (20130101) |
Current International
Class: |
D04H
1/72 (20060101); B27N 3/14 (20060101); D04H
1/70 (20060101); B27N 3/08 (20060101); B29c
013/00 (); B29j 005/00 () |
Field of
Search: |
;425/80,83,141
;264/91,109 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Spicer, Jr.; Robert L.
Attorney, Agent or Firm: Philpitt; Fred C.
Claims
I claim:
1. In the known apparatus for producing a web of dry fibers and
comprising a suction box structure having a substantially
rectangular top opening, a movable belt-like and gas-permeable
screen extending over said top opening of the suction box
structure, a hood-like cover extending over said top opening of the
suction box structure and above the screen to form a fiber
distribution chamber in which said screen forms a substantially
horizontal bottom, said distribution chamber having a fiber inlet
opening vertically spaced from said movable screen, means for
moving said screen longitudinally over said top opening of the
suction box structure, a vertical shaft communicating at its upper
end with said fiber inlet opening of the distribution chamber,
means for creating a flow of gas upwardly through said vertical
shaft, into said distribution chamber, downwardly through said
screen and out through said suction box structure, means for
suspending fibers in the gas stream rising through said vertical
shaft, the improvement which comprises:
said vertical shaft being generally rectangular in horizontal cross
section and extending across the full width of said distribution
chamber and being separated from said distribution chamber by a
substantially upright partition wall member extending transversely
of the running direction of said screen, said partition wall member
forming the rear wall of the distribution chamber, said
distribution chamber having a section extending in the running
direction of said screen that resembles a sector of a circle, of
which one bounding radius is represented by said screen, the other
bounding radius is represented by said partition wall member and
the arc is represented by a curved wall member forming part of said
hood-like cover, said curved wall member being extended beyond the
upper edge of said partition wall member to form a substantially
horizontal top cover for said vertical shaft and being vertically
spaced from said partition wall member so as to define with the
latter and above the same an opening extending in a vertical plane
and representing said fiber inlet opening of the distribution
chamber, a slot-like gas inlet opening being provided at the upper
end of said vertical shaft and horizontally opposite to said fiber
inlet opening for the introduction of a second stream of gas in a
substantially horizontal direction across the upper portion of said
vertical shaft and immediately beneath said horizontal top cover
thereof and into said distribution chamber.
2. An apparatus according to claim 1, wherein said slotlike gas
inlet opening for the introduction of the second gas stream is
variable as to its size.
3. An apparatus according to claim 2, wherein said slotlike gas
inlet opening is variable as to its configuration.
4. In the known apparatus for producing a web of dry fibers and
comprising a suction box structure having a substantially
rectangular top opening, a movable belt-like and gas-permeable
screen extending over said top opening of the suction box
structure, a hood-like cover extending over said top opening of the
suction box structure and above the screen to form a fiber
distribution chamber in which said screen forms a substantially
horizontal bottom, said distribution chamber having a fiber inlet
opening vertically spaced from said movable screen, means for
moving said screen longitudinally over said top opening of the box
structure, a vertical shaft communicating at its upper end with
said fiber inlet opening of the distribution chamber, means for
creating a flow of gas upwardly through said vertical shaft, into
said distribution chamber, downwardly through said screen and out
through said suction box structure, means for suspending fibers in
the gas stream rising through said vertical shaft, the improvement
which comprises:
said vertical shaft being generally rectangular in horizontal cross
section and extending across the full width of said distribution
chamber and being separated from said distribution chamber by a
substantially upright partition wall member extending transversely
of the running direction of said screen, said partition wall member
forming the rear wall of the distribution chamber, said
distribution chamber having a section extending in the running
direction of said screen that resembles a sector of a circle, of
which one bounding radius is represented by said screen, the other
bounding radius is represented by said partition wall member and
the arc is represented by a curved wall member forming part of said
hood-like cover, said curved wall member being extended beyond the
upper edge of said partition wall member to form a substantially
horizontal top cover for said vertical shaft and being vertically
spaced from said partition wall member so as to define with the
latter and above the same an opening extending in a vertical plane
and representing said fiber inlet opening of the distribution
chamber, an adjustable slot-like gas inlet opening being provided
at the upper end of said vertical shaft and horizontally opposite
to said fiber inlet opening for the introduction of a second stream
of gas in a substantially horizontal direction across the upper
portion of said vertical shaft and immediately beneath said
horizontal top cover thereof and into said distribution chamber,
said arc-forming, curved wall member having at least one inlet
opening located approximately midway between the ends of the arc
formed thereby, said at least one gas inlet opening being provided
for the introduction of an additional stream of gas in a mainly
downward direction through said distribution chamber towards said
movable screen.
5. An apparatus according to claim 4 wherein each of said at least
one gas inlet opening of the distribution chamber is variable as to
its size.
6. An apparatus according to claim 4 wherein each of said at least
one gas inlet opening of the distribution chamber is adjustable as
to its position.
7. An apparatus according to claim 4 wherein each of said at least
one gas inlet opening of the distribution chamber is variable as to
its configuration.
8. An apparatus according to claim 7 wherein individually
adjustable damper means are provided adjacent each of said at least
one gas inlet opening of the distribution chamber to vary the size
and configuration thereof.
9. An apparatus according to claim 8 wherein means for sensing the
thickness of the fiber web formed on said movable screen are
provided at points distributed transversely of said screen and
actuating means are provided for adjusting the setting of said
damper means in accordance with the input to said thickness sensing
means.
10. An apparatus according to claim 4 wherein the running direction
of said movable screen is reversible.
11. An apparatus according to claim 4 wherein said distribution
chamber is provided with a roller that is movable towards and away
from said screen and adapted to ride on said fiber web, and a
hinged flap connected in sealing engagement with a transverse wall
member of said distribution chamber rests on said roller.
12. An apparatus according to claim 4 wherein said open box under
said movable screen is a suction box and said means for creating a
flow of gas is a suction source connected to said box.
13. An apparatus according to claim 4 wherein said means for
suspending fibers in the gas stream rising through said shaft
comprises a rotary disintegrator for breaking up collections of
tangled fibers and for throwing the freed fiber into said vertical
shaft and wherein the lower end of said vertical shaft is connected
to a chamber, at the bottom of which conveyor means are provided
for removing residues of fiber material which the rising stream of
gas in said shaft is unable to carry upwardly into said
distribution chamber.
Description
This invention relates to the manufacture of more or less felted
fiber products from natural or artificial fibers, such as wood
fibers, textile fibers, glass and mineral wool fibers, asbestos
fibers and the like, and more particularly the invention is
concerned with the production of webs of such fibers on a
gas-permeable screen, commonly made of wire fabric, while applying
a so-called dry process in which flowing gas is used as a medium to
sort, transport and distribute the fibers. The dry process referred
to comprises two main steps, viz. first suspending the fibers in a
vertically rising gas stream and subsequently distributing the
suspended fibers over a gas-permeable screen that is advanced at
the bottom of a so-called distribution chamber and has its
underside exposed to a negative pressure, the rising fiber-carrying
gas stream being admitted into the distribution chamber in a
substantially horizontal direction.
As compared to the wet processes hitherto most commonly applied to
making paper or similar web-type fiber products, the use of a gas
instead of water or other liquid as a suspension medium for the
fibers to be distributed over a wire offers many advantages. This
is true not only fromm the viewpoint of safe-guarding the
environment but in particular in those cases where the fibers
themselves contain liqud-soluble matters which would contaminate
the water or where the fibrous material for one reason or the other
is intermixed with soluble impurities that are difficult to remove.
In addition, the wet process commonly requires preparatory drying
of the produced web, before the latter can be subjected to the
pressing, with or without heating, which is usually required for
finishing the product. Also, the wet process is objectionable, when
it is desirable e.g. to impregnate the fibers or to cover them with
adhesive before the web is being formed, because in such a case
large quantities of impregnating agent or adhesive will be lost in
the carrier liquid.
Although the dry process for the production of webs of more or less
felted fibers as referred to hereinbefore has been known for more
than half a century, it has only rarely, if at all, been applied in
practice. Instead great efforts have been made to develop rather
complicated mechanical means for strewing dry fibers over a moving
wire without letting them become sorted and literally transported
by a gas stream. So far the practical results of these efforts have
been unsatisfactory for several reaons. Among other things, it has
been found very difficult with the strewing method to meet the
requirements as to uniformity in thickness of the produced web, and
it is almost impossible to obtain that controlled distribution of
finer and coarser fibers in the thickness direction of the web,
which is frequently important in order to give the product the
desired properties.
Already when the first attempts were once made to substitute a
gaseous medium, such as air, for water as a fiber carrier in the
distribution of loose fibers over a movable wire, a vertical shaft
or duct was used, in which a rising gas stream was created and
caused to carry along fibers that in one way or the other were
spread or thrown into the gas stream. Almost from the beginning, it
was also suggested that the rising fiber-carrying gas stream should
be deflected in a substantially horizontal direction and then be
admitted into a distribution chamber, where the fibers were
permitted to fall down towards an endless wire or screen that was
advanced over a suction box at the bottom of the distribution
chamber. Unfortunately, great difficulties came up when this basic
idea should be put into practice. Firstly, it was found that the
fibers were swept away rather irregularly by the gas stream and had
a great tendency to get stuck and deposit in the duct connecting
the vertical shaft to the distribution chamber. Secondly, it was
difficult to obtain a uniform distribution of the fibers on the
wire or screen, before all in the transverse direction thereof, and
also to adjust the thickness of the fiber web formed on the wire in
a sufficiently reliable manner.
Accordingly, it is the object of this invention to offer a simple
and practical solution of these specific problems. With these and
other objects in view the invention consists, primarily, in a
method of distributing fibers suspended in a vertically rising gas
stream over a gas-permeable screen being advanced at the bottom of
a distribution chamber and having its underside exposed to a
negative pressure, the rising fiber-carrying gas stream being
admitted into the distribution chamber in a substantially
horizontal direction. The invention also consists in an improved
apparatus for producing fiber webs in a dry process by carrying out
the beforementioned method. Basically, the invention overcomes the
inconveniences referred to hereinbefore by suggesting that
additional gas streams should be used for controlling the
fiber-carrying gas stream as it enters the distribution chamber
from the vertical shaft or duct, and also for controlling the
pattern according to which the fibers are distributed and deposited
over and on the wire or screen within said distribution
chamber.
For a more complete elucidation of the invention an embodiment
thereof will be described in the following and with reference to
the accompanying drawing. In the drawing
FIG. 1 shows a slightly diagrammatic sectional elevation of an
apparatus embodying the invention and useful for distributing
fibers suspended in a gas stream over a movable, endless wire or
screen, while
FIG. 2 is a fragmentary front view of the apparatus as seen from
the line II--II in FIG. 1.
The section in FIG. 1 is taken in the running direction of the
wire, and it shold be understood that the wire can, of course, have
any desired width, whereas the width of the fiber distributing
means forming part of the apparatus can be adapted either to the
entire width of the wire or to the width of a selected part
thereof, if it is desirable to form a fiber web that is narrower
than the wire itself. In practice, this means that the apparatus
shown in FIG. 1 usually has a considerably larger extension
perpendicularly to the plane of the drawing than in this plane.
Referring to FIG. 1, an endless, flexible and gas-permeable screen
1, suitably of close-meshed wire cloth, runs over conducting and
supporting rollers 2, 3 and 4 and passes over an upwardly open
suction box 5, the interior of which is connected to a suction
source, not shown, e.g. in the form of a suction ventilator having
a relatively large capacity, so that a negative pressure can be
maintained in the suction box under the wire 1. Suitable means, not
shown, are provided for driving the wire at a preferably adjustable
speed. Above the section of the wire that passes over the suction
box there is arranged a distribution chamber, generally designated
by 6 and extending transversely over the wire. Accordingly, the
wire 1 forms a substantially horizontal, movable bottom of a
generally rectangular shape in the distribution chamber. In FIG. 1
the wire 1 is supposed to move from the left to the right as
indicated by an arrow but, as it will appear from the following, it
is also possible to reverse the moving direction thereof in order
to achieve special productional results. The required seal between
the wire 1 and the wall portions of the distribution chamber 6
extending across the wire is obtained by means of rollers 7 which
are movable towards and away from the wire and against which lean
sealing flaps 8 hinged to the outer sides of the respective
distribution chamber walls. One of the rollers 7 will then come to
roll in direct engagement with the wire 1, as shown to the left in
FIG. 1, whereas the other one will roll on top of the fiber web 9
formed on the wire, as shown to the right in FIG. 1.
The distribution chamber 6 has a vertical cross-section as seen in
the running direction of the wire, FIG. 1, that generally takes the
form of a sector of a circle, the one bounding radius of said
sector being represented by the section of the wire 1 extending
over the suction box 5, the other bounding radius being represented
by a vertical wall member 10 extending across the wire, and the
bounding arc being represented by a curved cap or hood 11. The
latter forms the top and the right hand wall of the distribution
chamber 6 and has approximately at the middle of its arc, a
slot-shaped opening 12 extending in the entire width of the
distribution chamber, i.e., perpendicularly to the plane of the
drawing. This elongate opening 12 is provided with an upper
adjustable damper plate 13 extending along the entire length
thereof and also with a horizontal series of lower damper plates 14
mounted adjacent each other in successive order and being
individually adjustable in the direction towards and away from the
upper damper plate 13 for varying, section by section, the width
and, hence, to a certain extent also of the configuration of the
opening 12, as can be seen from FIG. 2. By adjusting the damper
plate 13, the general size of the opening 12 and to a certain
extent also the angular position thereof in the hood 11 can
obviously be varied. The opening 12 puts the interior of the
distribution chamber 6 in communication either with the external
air as shown, or with a duct for closed delivery of gas, not
shown.
The upper part or top of the hood 11 is extended towards the left
beyond the wall member 10 and is separated from the upper edge of
the latter by an opening 15 that in the plane of the wall member 10
is rectangular and has a length corresponding to the width of the
distribution chamber 6 across the running direction of the wire 1.
The portion or extension 11' of the hood 11 projecting outside the
wall member 10 forms an upper, substantially flat and horizontal
top cover for a shaft or vertical duct 16 of substantially
rectangular horizontal cross section, said shaft having also a
length corresponding to the width of the distribution chamber 6.
The uppermost portion of the wall member 10 is common to both the
shaft 16 and the distribution chamber 6, i.e., the wall member 10
forms a partition between the shaft and the distribution chamber.
The shaft 16 and the distribution chamber 6 also have a common end
walls 17 which in the illustrated form of apparatus extend
downwardly on each one side of the wire 1 and, in fact, represent
the supporting end walls of the entire apparatus. The vertical
shaft 16 is, on the side facing away from the distribution chamberr
6, bounded by a vertical wall member 18, the upper edge of which is
spaced from the hood extension 11' by a slot-shaped opening 19
extending horizontally between the end walls 17. The size of this
opening is variable by means of a vertically adjustable damper
plate 20. If desired, this single damper plate may be replaced by a
series of smaller damper plates resembling the damper plates 14
previously described, and in such a case not only the size but also
the configuration of the opening 19 may be varied, which sometimes
can be advantageous. It is also possible to make and attach the
damper plate 20 in such a manner that the configuration of the
opening 19 can be varied by tilting the damper plate in the plane
of the wall member 18.
The vertical shaft 16 has its lower end connected to a chamber 21,
at the bottom of which there is arranged a conveyor screw 22 for
the removal of any such fiber material that is not carried upwards
by the gas stream passing through the chamber 21 and the shaft 16.
The chamber 21 has a gas inlet opening 23 through which the main
flow of air or gas enters the apparatus and the size of which is
variable by means of an adjustable damper device 24. Like the
opening 19, referred to above, the gas inlet opening 23 can be
connected to the external air, as shown, or both openings can
communicate with a closed gas delivery duct e.g. from the suction
source, if a closed gas circuit is desired.
Outside the wall member 18 is a feed chute 25 into which more or
less matted together fiber bundles are supplied at a suitable,
preferably adjustable rate such as by means of a belt conveyor
indicated at 26. At the lower end of the feed chute 25 there is
mounted a rotary disintegrator 27 in the form of a roller having a
plurality of radially projecting pins thereon. This roller is
rotated in the clockwise direction at a rather high speed for
disintegrating the fiber bundles received in the chute 25 and for
throwing out the separated, free fibers into the lower part of the
shaft 16 and into the chamber 21 from which the shaft proceeds
upwards. Usually, a small amount of air also enters the apparatus
through the feed chute 25, but this can be avoided, if desired, by
delivering the fiber bundles into the chute through an air lock
arrangement well known in itself but not shown.
The fiber bundles received in the feed chute 25 are broken up by
the rotating disintegrator 27 and the free fibers are caught and
carried along upwards by the gas stream passing through the chamber
21 and rising through the shaft 16. Such fiber material that, for
one reason or another, is not carried away by the rising gas
stream, gathers at the bottom of the chamber 21 and is removed by
means of the conveyor screw 22 which, of course, can be replaced by
any other suitable feeding-out device. The removed residue of the
fiber material may, if desired, be returned to the feeding-in
conveyor 26. The feed chute 25 and the disintegrator 27 have a
length corresponding to the length of the chamber 21 and that of
the horizontal cross-section of the shaft 16, whereby a good
distribution of the fibers in the entire shaft is achieved. In the
chamber 21 an important fiber sorting will take place, whereby
heavy fibers as well as unresolved fiber bundles and at least
certain heavy impurities become separated, because the rising gas
stream is unable to carry them upwards through the shaft 16.
As a result of the fact that air is admitted into the upper end of
the shaft 16 immediately below the hood extension 11' through the
opening 19, the deflection of the fibre-carrying gas stream through
the opening 15 into the distribution chamber 6 is greatly improved.
In addition, the fact that the wall member 10 forms only a thin
partition between the distribution chamber and the shaft 16 assists
in preventing uncontrolable fiber-deposits. The second gas stream
admitted through the opening 19 causes the fiber-carrying vertical
gas stream to follow a path resembling a trajectory when entering
the interior of the distribution chamber and continuing towards the
wire 1. By adjusting the size of the opening 19, the thickness of
the fiber web 9 formed on the wire 1 can be controlled within
rather wide limits. Itt should be noted, however, that also the
amount of fiber material supplied to the apparatus per time unit,
as well as the running speed of the wire are factors involved in
determining the average thickness of the fiber web formed. By
varying the configuration of the opening 19, the thickness of the
fiber web formed on the wire 1 may be controlled in the transverse
direction of the latter to a certain degree. Such transversal
thickness control is, however, accomplished with better accuracy by
means of the additional gas stream entering the upper part of the
distribution chamber 6 through the opening 12. This will result
from the fact that the lastmentioned gas stream, although having a
main direction from above and downwards in the distribution
chamber, will also have a certain component of movement in a
direction which more or less crosses the fiber-carrying gas stream
and thereby disturbs its trajectory.
By sensing the thickness of the fiber web 9 in a plurality of
points spaced in the transverse direction of the wire 1 by means of
sensing means indicated at 28, which is suitably done slightly
before the fiber web is leaving the distribution chamber 6, and by
letting these sensing means 28 govern the operation of small
actuators 29 adjusting the positions of the lower damper plates 14,
possible tendencies of thickness variations in the fiber web can be
inhibited, so that, from a practical point of view, a uniform
thickness of the fiber web is achieved over the entire width of the
wire 1. If, on the other hand, it is desirable to produce a fiber
web having a thickness that varies in the transverse direction of
the wire 1, a similar control may be used, of course, in order to
obtain a desired corrugation of the upper side of the fiber web. In
fact, the possibility of varying andd correcting the thickness of
the fiber web in the way described is very striking and
surprising.
The gas-suspended fibers entering the distribution chamber 6
through the opening 15 will follow a trajectory starting in a
substantially horizontal direction. As known per se, this will
result in a certain and frequently very desirable separation or
sorting of the fibers according to size and weight. More
particularly, the coarser and heavier fibers will be thrown farther
away from the entrance opening 15, while the finer and lighter
fibers will be sucked down the shortest way towards the wire 1,
i.e., be deposited on the wire closer to the wall member 10. This
effect can, if desired, be utilized for achieving a certain
stratification of differently sized fibers in the fiber web. Thus,
if the wire 1 is driven as illustrated in FIG. 1 from the left to
the right, the lighter and finer fibers will collect at the bottom
of the fiber web, closest to the wire, while the heavier and
coarser fibers will be deposited on top of the lighter ones.
However, by reversing the running direction of the wire 1
approximately the opposite result may be achieved. On the other
hand, the stratification effect may to a certain degree be
controlled by more or less disturbing the flow of gas inside the
distribution chamber 6 which is also effected by means of the gas
streams entering through the opening 12. If a very marked
disturbance of this kind is desirable, additional gas-admitting,
slot-shaped openings may be provided in the hood 11, preferably
above the opening 12. It is also possible to change the position of
the opening 12 in the hood in order to vary the distribution
pattern of the fibers.
As should be apparent from the foregoing description the invention
offers surprising possibilities for the control and variation of
the operation of the apparatus, whereby the advantages of the basic
operating principle may be fully utilized. The apparatus itself is
nevertheless relatively simple from a structural point of view and,
before all, it is reliable in operation and capable of producing
fiber webs of a high quality and of a great accuracy in thickness
at a high speed from most types of fibers which at all lend
themselves to transportation by means of gas streams.
* * * * *